1. Field of the Invention
This invention relates to an instrument for debonding orthodontic brackets from teeth.
2. Description of the Related Art
A widely used tool for removing orthodontic brackets from teeth is described in U.S. Pat. No. 4,553,932, owned by the assignee of the present invention. The tool in U.S. Pat. No. 4,553,932 includes an L-shaped body with a handle and a pair of spaced apart abutments which straddle the bracket on occlusal and gingival sides to engage the tooth. The tool also includes a second class lever pivotally attached to the body, and the lever is connected to a single length of wire having a loop adapted to engage a single tie wing of the bracket. By moving the lever relative to the body while the abutments contact the tooth, the loop exerts a rotational-type pulling force to peel one side of the bracket base away from the tooth while the other side of the bracket base is at least initially still in contact with the tooth.
While the tool described in U.S. Pat. No. 4,553,932 has performed satisfactorily for brackets made of metallic materials, newer brackets made of brittle material such as ceramics including polycrystalline alumina may fracture when subjected to a rotational or peeling-type of debonding operation. In addition, the wings of ceramic brackets are much more susceptible to breakage while in tension during a debonding operation than wings of a comparable size of a metal bracket. For these reasons, the tool described in U.S. Pat. No. 4,553,932 has not been widely used in connection with ceramic brackets.
In the past, attempts have been made to remove ceramic brackets by a plier-like tool having a pair of opposed jaws with sharpened tips. In use, the tips are placed adjacent to the bonding adhesive between the base of the bracket and the tooth, and the tool is then squeezed to urge the tips together and pry and lift the bracket on both sides from the tooth. This type of debonding operation, however, may damage enamel on the tooth surface when the tips of the tool slide in wedging fashion across the tooth and beneath the bracket.